Ribbon tensioning mechanism for high speed printers



United States Patent O 3,099,299 RIBBON TENSIONING MECHANISM FOR HIGHSPEED PTERS George E. Comstock 3d, Huntington, N.Y., assignor to PotterInstrument Company, Inc., Plainview, N.Y., a corporation of New YorkFiled June 2, 1961, Ser. No. 114,432 1 Claim. ((31. 101-100) The presentinvention concerns high speed drum printer ribbons and lateraltensioning means for such ribbons.

The present invention is generally applicable in high speed lineprinters in which a separate type font is presented in each printingposition during each printing cycle. The type fonts are arrangedcircumferentially on a cylindrical drum whose axis lies parallel to theplane of the paper on which the information is to be printed, said axisbeing oriented perpedicular to the direction of the feed motion of thepaper. A multiple, parallel hammer assembly is mounted on the oppositeside of the paper from the type drum, and so oriented that when thehammer is actuated, it depresses the paper into tangential contact withthe character then present at the impact line.

An inked ribbon is inerposed between the paper and the type drum wherebyan image of the type character impacted is transferred to the paper. Theribbon extends across the full axial length of the print drum and ismoved or fed in a direction parallel to the motion of the paper. Theconditions of operation of such ribbons are so severe that it is notunusual for a ribbon to require replacement after only a few hours use.This ribbon deterioration is produced by the severe mechanical action onthe ribbon due to the hammer impact and the simultaneous sliding motionof the type face during con-tact. This action tends to crush the fibersof the ribbon and to stretch and distort the fabric. As a consequence,after a short period of usage, the ribbon becomes baggy and diflicult tocontrol. Ribbons are made of woven textile fabrics which inherentlypossess very low resistance to shearing distortion, making it difficultto preserve linear tracking of the ribbon, particularly when all or aportion of its width be comes mechanically distorted or damaged.

Guidance of these ribbons by means which are successful with other mediasuch as flat belts, paper tape, or Mylar tapes, all of which possessshear stiffness, are not generally successful with fabric ribbons. Forexample, if one attempts to use flanged rollers or flanged guide poststo control the edge locus, one finds a tendency for the edge of theribbon to roll or fold over on itself as soon as any significant lateralforce is developed between the edge of the ribbon and the guide flange.Crowned or tapered rollers are not the solution either, because theabsence of shear stiffness prevents a fabric ribbon from developingtracking forces on a crowned roller such as occurs with stiffer media.

Accordingly, the present invention consists in providing a stiff edge onthe ribbon beyond the area Where printing takes place, and inperforating this stiif edge with regularly spaced holes to engagedriving and guiding sprockets. According to a preferred form of thepresent invention two pairs of sprockets are utilized one ahead of andthe other behind the printing zone. One sprocket of each pair arecoupled together so that they rotate in unison. The second sprocket ineach pair is axially spring loaded away from its companion in order toapply lateral tension to the ribbon. in this way the movement of theribbon is such as to prevent differences in the accumulated movement atthe two edges of the ribbon, and therefore to constrain the ribbon totrack in the desired 3,990,299 Patented May 21, 1963 path. Also, thetensioning of the ribbon in the printing area reduces the difficultiesassociated with sagging in this region.

According to the present invention the edge stiffening may be providedby one of a number of methods. One satisfactory method is to cementstainless steel strips of the order of .002 thick to the edges of theribbon by means of thermo-setting epoxy adhesive. Other methods includecementing shear resistant material such as paper or Mylar to the edgesof the ribbon. Another method consists in weaving heavier threads alongthe edges with a tighter weave and filling these areas with suitablestiifening filler such as starch or glue. It is preferred that thesprocket holes are accurately punched with holes of each pair lying on acommon centerline lying straight across the ribbon after the reenforcededges have been formed. The inking is also preferably carried out afterthe reenforcing steps have been performed.

Accordingly, one object of the present invention is to provide methodsof and means for improving high speed printer ribbons and the handlingthereof.

Another object is to provide reenforcement of high speed printerribbons.

A particular object is to provide improved high speed printer ribbons byproviding reenforced, sprocket hole containing edges in such ribbons.

A still further object is to provide synchronized and laterallytensioned sprockets for handling edge reenforced and perforated highspeed printer ribbons.

These and other objects will be apparent to those skilled in the artfrom the detailed description of the invention given in connection withthe various figures of the drawing.

In the drawing:

FIGURE 1 is a view of a section of drum printer ribbon in accordancewith the present invention.

FIGURE 2 is a diagrammatic representation of the essential components ofa drum printer utilizing the present invention.

FIGURE 3 is a typical ribbon sprocket constructed in accordance with thepresent invention.

FIGURE 4 is a plan view of portions of a drum printer in accordance withthe present invention.

In FIG. 1 is shown a fabric ribbon 1 provided with reenforced edges 2and 3 punched with uniformly spaced sprocket holes 4 and 5. Thereenforcements along the edges 4 and 5 may be strips of thin metal,paper, Mylar or other stilfening material cemented to the ribbon or theedges may be stiffened by utilizing heavier fibers in the fabric withthe addition of glue or other stiffening agent. The uniformly spacedsprocket holes are punched in the stiffened edges in rows aligned sothat holes on opposite edges fall on parallel lines across the ribbonand perpendicular to its edges.

FIG. 2 shows how this ribbon is used in a drum printer and how axiallyspring loaded sprockets are used to pull the ribbon across the surfaceof the character drum in the printing area. Character type carryingprinting drum 11 carried on shaft 12 is rotated by suitable means (seeFIG. 4) and is utilized for printing on a printing sheet 8 when hammers15 of hammer assembly 14 are energized to squeeze the printing sheetthrough ribbon 1 against type faces 13 on the surface of drum 11. Ribbon1 is moved between take-up reel 6 carried on shaft 7 and take-up reel 20carried on shaft 21 under precise control of sprockets 9 and 10' onshaft 18 and sprockets 16 and 17 on shaft 19 as Will be set forth inmore detail in connection with FIG. 4.

The preferred form of the spring loaded sprocket in accordance with thepresent invention is shown in FIG. 3. Sprocket shaft 23 carries sprocket28 secured to the shaft and sprocket 22 which is free to slide axiallybut is keyed to shaft 23 by key '24 so that both sprockets are turned byshaft 23- and sprocket teeth 25 and 29 are aligned and moved,insynchronism. Sprocket 22 is urged axially and away from-sprocket 28 bymeans of spring '27 bearing against collar'26.' when this sprocketassembly is used, as in FIG. 2, to pull the printer ribbon it keeps theunder lateral tensio'nfand thereby overcomes any tendency to sag ordeform'dueto tliepounding it experiences from the hammers.

FIG. 4 is a top view of a printer system in which type drum ll'isrotated by motorf30 over shaft' 12. Motor power is supplied over leads3738 connected to a suitable power source not shown, The ribbon drivesprockets are driven from shaft 12 bysuitable means such as 'chain 32driven by sprocket 33 to drive sprocket 31 and chain 35 passing betweensprockets '34'a'nd 36. Suitable speed and direction may be determinedbysuitable gears contained'in planetary'driv'e '45 on shaft 12. The ribbontake-up spools 6 and 20 are turned by suitable slipping drives such asspring belt 44- passing between pulleys 42 and 43 and spring belt 41passing between pulleys In operation ribbon 1 is moved under precisecontrol of synchronized sprockets 9-10 and 16-17 and under lateraltension due to the sprocket'longitudinal springs (FIG. 3). This controland tensioning provideshan dling of the large ribbons required in-suchdrum printer systems without permitting creasing or rolling of the edgesand also with minimum sag and other undesirable distortions. t

It will be seen that while the ribbon construction and the ribbonhandling devices according to the present invention have been shown anddescribed in combination with a drum printer for which they areparticularly adapted, that they may also -beused' to advantage in otherhigh speed printers as, for example, in chain or belt type printers. Infact they are adapted for use generally where unusual stresses may beplaced on printing ribbons and particularly Where the ribbons areunusually wide.

While only a single embodiment of the present invention has been shownand described, modifications will be apparent to those skilled in theart and within the spirit and scope of the invention as set forthspecifically in the appended claim.

What is claimed is:

In a system for moving a printing ribbon over the printing area of aprinter apparatus and the like, the combination including, a printingstation having hammers and type font, printing ribbon storage meanslocated relative to said printing station to permit a ribbon to be fedcontiguously past the printing station, a printing ribbon includingperforations at the edges for engaging sprocket means, and ribbon feedmeans "including tensioning means comprising at least two shaftsjournaled transverse of the direction of feed for said ribbon onopposite sides of said printing station, first and second sprocket meansrotatably fixed on each shaft, corresponding sprocket means beingslidable freely on each respective one of said shafts, and resilientmeans continually acting against each respeotive one of said slidablesprocket means in a direction away from the other sprocket means so thata printing ribbon is maintained under a substantially uniform, lateraltension.

References Cited in the file of this patent UNITED STATES PATENTS127,731 Bailey June 11, 1872 1,953,316 Stark Apr. 3, 1934 2,066,687Hudspeth Jan. 5, 1937 2,307,108 Bryce Jan. 5, 1943 2,339,199 Smith Jan.11, 1944 2,627,807 Buhler Feb. 10, 1953 2,630,901 Johnson et a1 Mar. 10,1953 2,940,385 House June 14, 1960 FOREIGN PATENTS 21,018 Great BritainNov. 17, 1910 28,619 Norway Nov. 25, 1918

